Filling an aquarium tank

An aquarium tank can hold 7700 liters of water. There are two pipes that can be used to fill the tank. The first pipe alone can fill the tank in 77 minutes. The second pipe can fill the tank in 44 minutes by itself. When both pipes are working together, how long does it take them to fill the tank?

Solution Preview

In one minute, the fraction of the tank that the first pipe can fill = 1/77